The present invention relates to hydraulic fluid power steering systems having an accumulator for supplying fluid in the event that the vehicle engine or primary fluid pressure source fails and more particularly relates to improvements in the system disclosed in co-pending application, Ser. No. 196,199, filed on Oct. 14, 1980 by Gage et al and assigned to the same assignee as is the instant application.
A power steering system disclosed in the above-identified patent application includes an emergency steering valve coupled to an accumulator, to a steering fluid pressure supply pump and to a main steering control valve and comprises a pressure-responsive valve spool which occupies a normal or closed position wherein it prevents the discharge of fluid from the accumulator when the system pressure is above a predetermined minimum value and automatically shifts to an emergency or open position wherein it permits fluid to discharge from the accumulator to the main steering valve when the system pressure decreases to the predetermined minimum value. When the valve spool shifts to its emergency position, it completes an electrical circuit to an indicator which apprises the operator that the steering system is operating in an emergency steering mode. One drawback of this electrical circuit is that it requires a resistor which acts as a source of constant power drainage. Another drawback is that the valve spool may oscillate in response to pressure surges and effect a premature activation of the emergency steering mode indicator.